It is known to make tert-amine oxides by reacting tert-amines with aqueous hydrogen peroxide Murata et al. U.S. Pat. No. 4,247,480 teach that the reaction rate can be increased by adding carbon dioxide to the reaction mixture. This necessitates injecting a gas which requires gas handling facilities. It would be desirable to be able to promote the reaction rate without the necessity of using additional equipment.